Butterfly valve

ABSTRACT

In this butterfly valve (10) provided with: a main body (11); valve shafts (13, 14); and a valve body (30) that is rotatable with respect to the main body, the valve body is formed integrally from a core material (32) and a contour forming member (31) that is formed from a synthetic resin material and that encircles the core material and forms the contour of the valve body. The valve body has bearing holes (33, 34) that support the valve shafts, the contour forming member has a bearing inner peripheral part (36) that forms at least a part of the inner peripheral surface of each of the bearing holes, the contour forming member is formed continuously with the bearing inner peripheral part, and the core material has a bearing reinforcing part (35) that supports the bearing inner peripheral part of the contour forming member, radially outside from the rotation axis of the valve body.

This application is a Continuation of U.S. patent application Ser. No.16/319,267, filed on Jan. 18, 2019, which is a National StageApplication of PCT/JP2017/026141, filed Jul. 19, 2017, which claimsbenefit of Japanese Patent Application No. 2016-142416, filed Jul. 20,2016, which applications are incorporated herein by reference. To theextent appropriate, a claim of priority is made to each of theabove-disclosed applications.

FIELD

The present invention relates to a butterfly valve having a valve bodycontaining a core member inside.

BACKGROUND

A butterfly valve is used for controlling the flow of hydrochloric acidor other corrosive fluid. To raise the corrosion resistance and chemicalresistance of such a butterfly valve, the past practice has been to formthe valve body from a plastic material. Further, in recent years, largersizes of butterfly valves with valve bodies formed from plasticmaterials and higher temperatures of the ranges of usage temperatureshave been particularly sought. However, with a valve body made of aplastic material, as the temperature of the fluid circulating throughthe butterfly valve rises or as the size of the butterfly valve becomeslarger, it gradually becomes more difficult to obtain the requiredstrength. In particular, when the valve body is a type supported by avalve shaft divided into two parts, the stress occurring at the bearinghole of the valve body supporting the valve shaft becomes higher and asa result sometimes the problem arises of the bearing hole deforming.

To deal with the above-mentioned problem, as described in PTL 1, theconventional practice has been to reinforce a plastic valve body with ametal core member sealed inside it.

CITATION LIST Patent Literature

[PTL 1] Japanese Patent No. 3877885

SUMMARY Technical Problem

The valve body of the butterfly valve of PTL 1 is reinforced by a coremember made of a metal arranged inside of it, but would appear to beunable to be used for controlling the flow of a corrosive fluid. That isto say, the valve body of PTL 1 is covered by a plastic material in themajor part of the outside surface, including the opening edge of thebearing hole, but the metal core member is exposed at the bearing holeinto which the fluid may flow. Note that, a bearing hole is usuallysealed by a seat ring or other seal member and the opening edge of thebearing hole, but often the plastic opening edge deforms due to a hightemperature or aging resulting in the seal of the bearing hole beingbroken.

The present invention is made in consideration of the above situationand has as its object the provision of a butterfly valve having a valvebody provided with strength, corrosion resistance, and chemicalresistance.

Solution to Problem

To realize the above-mentioned object, according to the presentinvention, there is provided a butterfly valve comprising a main body,valve shaft, and valve body able to rotate with respect to the mainbody, wherein the valve body is integrally formed from a core member anda contour forming member made of a plastic material surrounding the coremember to form a contour of the valve body and has a bearing holesupporting the valve shaft, the contour forming member has a bearinginner peripheral part forming at least part of an inner peripheralsurface of the bearing hole, the contour forming member is continuouslyformed including also the bearing inner peripheral part, and the coremember has a bearing reinforcing part supporting the bearing innerperipheral part of the contour forming member from radially outside of arotational axis of the valve body.

Advantageous Effects of Invention

In the butterfly valve according to the present invention, at least partof the bearing hole of the valve body is formed by the bearing innerperipheral part made of a plastic material without the core member beingexposed, while the bearing inner peripheral part is supported by part ofthe core member, that is, the bearing reinforcing part, from radiallyoutside. For this reason, the part formed by the bearing innerperipheral part of the bearing hole has a sufficient corrosionresistance, while, even if controlling the flow of high temperaturefluid, it is resistant to deformation. As a result, when using that partto seal the fluid, a high sealing ability can be maintained. Further,the plastic material forming the bearing inner peripheral part isconnected with the surrounding plastic material. This also contributesto keeping the bearing hole from deforming.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front partial sectional view of a butterfly valve accordingto an embodiment of the present invention at the time of closing.

FIG. 2 is a perspective view including a partial cross-section of avalve body of the butterfly valve.

FIG. 3 is an enlarged view of a part A of FIG. 1.

FIG. 4 is a perspective view including a partial cross-section of a coremember contained inside the valve body.

FIG. 5 gives (a) a plan view and (b) a sectional view along B-B of acore member of a first modification of the embodiment of the presentinvention.

FIG. 6 is a front view including a partial cross-section of a top partof a valve body in the first modification.

FIG. 7 gives (a) a plan view and (b) a sectional view along C-C of acore member of a second modification of the embodiment of the presentinvention.

FIG. 8 is a front view including a partial cross-section of a top partof a valve body in the second modification.

FIG. 9 gives (a) a plan view and (b) a sectional view along D-D of acore member of a third modification of the embodiment of the presentinvention.

FIG. 10 is a front view including a partial cross-section of a top partof a valve body in the third modification.

FIG. 11 is a front sectional view of a top part of a valve body in afourth modification.

DESCRIPTION OF EMBODIMENTS

Below, referring to the attached drawings, a butterfly valve 10according to an embodiment of the present invention will be explained.

FIG. 1 is a front partial sectional view of a butterfly valve 10according to the embodiment of the present invention and shows the stateof the valve body 30 closing the flow path. This butterfly valve 10comprises a substantially ring-shaped main body 11 having projectingparts at two locations at the top and bottom, a disk-shaped valve body30, a top side first valve shaft 13 and bottom side second valve shaft14 arranged on a rotational axis R, a substantially cylindrically shapedseat ring 12 sealing a clearance between the main body 11 and the valvebody 30, plastic bushings 15 to which pluralities of O-rings 16 areattached and which are inserted over the valve shafts, a handle 17connected to the top side first valve shaft 13, a gear mechanism 18connected to it, and a valve shaft holder 19 arranged at a bottom of themain body 11 and supporting a bottom side second valve shaft 14 as maincomponents. Note that, in FIG. 1, the handle 17 and the gear mechanism18 are not shown in cross-section.

The main body 11 has body bearings 21, 22 at the top part and bottompart so as to support the inserted first and second valve shafts 13, 14to be able to rotate through the bushings 15. The main body 11 of thepresent embodiment is formed as a plastic molded part. Insidesurrounding the body bearings 21, 22, metal insert members 23 areincluded for reinforcement. The handle 17 connected to the top part ofthe main body 11 has the gear mechanism 18 for transmitting therotational torque of a horizontally extending handle shaft to thevertically extending first valve shaft 13. Note that, the gear mechanism18 is a conventional type of one comprised of a cylindrical worm and aworm wheel, so illustration of the inside is omitted. To transfer therotational torque applied to the handle 17 to the valve body 30 by thefirst valve shaft 13, the first valve shaft 13 is supported through thebushing 15 to be able to rotate by the main body 11 while is connectedto not be able to rotate with respect to the valve body 30. For thisreason, the horizontal cross-sections of the bottom end of the firstvalve shaft 13 and a later explained first small diameter hole 33 b ofthe valve body 30 in which this is inserted for engagement are formednoncircular. On the other hand, the second valve shaft 14 is supportedthrough the bushing 15 to be able to rotate with respect to the mainbody 11 and with respect to the valve body 30. Therefore, the secondvalve shaft 14 is formed to a circular horizontal cross-sectional shapeeverywhere.

FIG. 2 is a perspective view including a partial cross-section of thevalve body 30 of the butterfly valve 10 according to the presentembodiment. The valve body 30 is integrally formed from a plasticcontour forming member 31 forming a disk-shaped outside shape and ametal core member 32 surrounded by the contour forming member 31. Thevalve body 30 in the present embodiment is formed by injecting a plasticmaterial for forming the contour forming member 31 into a mold forinjection molding in which the core member 32 is preset. As the plasticmaterial, in the present embodiment, PVDF (polyvinylidene fluoride),which has a high chemical resistance, is used. However, in the presentinvention, embodiments in which other plastic materials, for example, PP(polypropylene), PVC (polyvinyl chloride), PE (polyethylene), PFA(perfluoroalkoxyalkane), etc., are used are also possible. On the otherhand, the core member 32 is formed from an aluminum alloy for castinguse in the present embodiment. However, the material of the core member32 is not limited to this. If having a mechanical strength higher thanthe contour forming member 31, it may be another metal material orfurther may be a nonmetallic material.

The valve body 30 has a first bearing hole 33 for supporting the topside first valve shaft 13 and a second bearing hole 34 for supportingthe bottom side second valve shaft 14. These first and second bearingholes 33, 34 are formed coaxially with the rotational axis R. The firstbearing hole 33 is comprised of a relatively large diameter first largediameter hole 33 a including an open end into which the bushing 15 isinserted and supporting the first valve shaft 13 through the bushing 15and a relatively small diameter first small diameter hole 33 b extendingfurther from the first large diameter hole 33 a to the inside in therotational axis R direction. The inner peripheral surface of the firstlarge diameter hole 33 a is formed by the contour forming member 31,while the inner peripheral surface of the first small diameter hole 33 bis formed from the core member 32. The bushing 15 is not inserted in thefirst small diameter hole 33 b. The tip side part of the first valveshaft 13 is directly inserted and fit into it. Further, in the presentembodiment, the horizontal cross-sectional shape of the first smalldiameter hole 33 b is formed into a noncircular double D-shape so thatrotational torque from the first valve shaft 13 can be transmitted, inother words, a shape with two facing arc parts of a circle replaced by achord.

The second bearing hole 34 is comprised of a relatively large diametersecond large diameter hole 34 a including an open end into which thebushing 15 is inserted and supporting the second valve shaft 14 throughthe bushing 15 and a relatively small diameter second small diameterhole 34 b extending further from the second large diameter hole 34 a tothe inside in the rotational axis R direction. The second large diameterhole 34 a is formed by the same structure and dimensions as the firstlarge diameter hole 33 a of the first bearing hole 33. On the otherhand, the second small diameter hole 34 b does not transmit rotationaltorque with the second valve shaft 14, so has a circular horizontalcross-sectional shape and differs from the first small diameter hole 33b of the first bearing hole 33 on this point.

The first bearing hole 33 and the second bearing hole 34 have similarconfigurations as explained above except that the first small diameterhole 33 b and the second small diameter hole 34 b differ in horizontalcross-sectional shapes. Below, the first bearing hole 33 will beexplained as a representative example. For the valve shaft, the firstvalve shaft 13 will be used as a representative example. Further, tosimplify the description, the ordinal “first” included in the names ofthe components will be omitted in the explanation. However, this doesnot apply when it is necessary to discriminate between the “first” and“second”.

Each bushing 15 in the present embodiment is made using polyvinylidenefluoride (PVDF) having high resistance to a corrosive fluid as amaterial. The bushing 15 is provided with the plurality of O-rings 16 sothat the fluid does not enter to the inside of the valve body 30 and sothat it does not touch the valve shaft 13. In particular, as shown inFIG. 3, four O-rings 16 are arranged at the part of the bushing 15inserted into the large diameter hole 33 a of the bearing hole 33.However, for example, if the valve shaft 13 is made from a materialhaving a high corrosion resistance and, therefore, fluid is allowed tocontact the valve shaft 13 and if rotational torque is allowed to act onthe O-rings, an embodiment not using the bushing 15 is also possible. Inthis case, O-ring-use grooves may be formed in the valve shaft andO-rings may be directly fit at the valve shaft. In actuality, the valveshaft 13 can be fabricated by lathe-turning, so it is also possible toselect as that material a material such as stainless steel having a highcorrosion resistance.

The inner peripheral surface of the large diameter hole 33 a of thebearing hole 33, as explained above, is formed by the contour formingmember 31. As shown in detail in FIG. 3, the cylindrically shaped partof the core member 32 is arranged radially outside from the innerperipheral surface of the large diameter hole 33 a. In the Description,the cylindrically shaped part 35 of the core member 32 is called the“bearing reinforcing part”. Further, a cylindrically shaped part 36 ofthe contour forming member 31 between the inner peripheral surface ofthe large diameter hole 33 a and the cylindrically shaped bearingreinforcing part 35 is called the “bearing inner peripheral part”. Thebearing reinforcing part 35 of the core member 32 is provided forreinforcing the bearing inner peripheral part 36. When the shear forceand bending moment generated at the valve body 30 based on the pressureacting from the fluid on the valve body 30 are supported by the largediameter hole 33 a, the force acting from the valve shaft 13 to thelarge diameter hole 33 a and bearing inner peripheral part 36 issupported by the bearing reinforcing part 35, so deformation of thebearing inner peripheral part 36 is suppressed and the seal with thebushing 15 by the O-rings 16 can be reliably maintained. In particular,in the present embodiment, the valve shaft 13 is supported by the smalldiameter hole 33 b as well, so it will be understood that the forceacting on the bearing inner peripheral part 36 is reduced more.

In this way, the bearing reinforcing part 35 greatly contributes to thesupport of the shear force and bending moment, so the wall thickness atthe bearing inner peripheral part 36 can be made thinner. As a result,it becomes possible to avoid an increase in the outside dimensions ofthe bearing hole 33 of the valve body 30 and the accompanying increasein the flow resistance at the time of valve opening. While not shown, ifviewed by a cross-section rotated from FIG. 3 about the rotational axisR by 90 degrees, the wall thickness at the bearing inner peripheral part36 is formed thinner than the wall thickness of the contour formingmember 31 at the outer circumferential side of the bearing reinforcingpart 35.

Next, referring to the perspective view including the partialcross-section of the core member 32 shown in FIG. 4, the core member 32will be explained below in further detail. The core member 32 has arod-shaped center part 37 extending along the rotational axis R and twomain reinforcing parts 38 extending substantially in the plane includingthe rotational axis R symmetrically to the left and right at the twosides of the center part 37. At the top end and the bottom end of therod-shaped center part 37, the above-mentioned bearing reinforcing parts35 are provided.

Each main reinforcing part 38 is comprised of five horizontal members 38a extending horizontally from the rod shaped center part 37 and twovertical members 38 b extending in the rotational axis R direction forconnecting these horizontal members 38 a—all formed in a lattice shape.The five horizontal members 38 a differ in lengths in accordance withthe outside diameter of the circle of the valve body 30 and further havebase parts substantially equal to the outside diameter of the centerpart 37 and are tapered to become narrower from the base parts to thetip parts. Since the core member 32 is formed in this way, a relativelylight weight and small material can be used to effectively support theforce acting from the fluid on the valve body 30.

The first small diameter hole 33 b of the first bearing hole 33 and thesecond small diameter hole 34 b of the second bearing hole 34 areconnected in the present embodiment by a vertical hole 39 extendingcoaxially with the rotational axis R. In this vertical hole 39 of thecore member 32, a metal pipe member 41 is buried. The material of thepipe member 41 has a higher vertical elastic modulus and tensilestrength than the material of the core member 32. Further, the pipemember 41, in the present embodiment, is cast in when casting the coremember 32 to be assembled into the core member 32. Due to this verticalhole 39 and pipe member 41, lightening of the weight of the core member32 and improvement of the casting ability can be realized withoutcausing a drop in strength of the core member 32. However, an embodimentof a core member where no vertical hole 39 is formed is also possible inthe present invention.

Each bearing reinforcing part 35, in the present embodiment, is providedwith a plurality of through holes 35 a connecting the inner peripheralsurface and the outer peripheral surface. These through holes 35 a areprovided so as to form passageways for plastic material forming thebearing inner peripheral part 36 when setting the core member 32 in amold (not shown) and injection molding the contour forming member 31. Atthe time of injection molding, the plastic material forming the bearinginner peripheral part 36 can flow into the cylindrically shaped cavityfor forming the bearing inner peripheral part 36 not only by routes fromthe outer circumferential side of the bearing reinforcing part 35 overthe end face, but also by routes running through the through holes 35 a.For this reason, even when the bearing inner peripheral part 36 is thinin thickness and therefore the width of the cavity is narrow or when thelarge diameter hole 33 a (and therefore the cavity) is deep in depth,the plastic material reliably flows into the cavity and the bearinginner peripheral part 36 can be formed without allowing insufficientfilling. In particular, when, like in the present embodiment, the coremember 32 is formed by a relatively small amount of material and thevalve body 30 is formed so that the ratio of the contour forming member31 in the valve body 30 becomes relatively large, it easily becomesdifficult for the plastic material to flow into the cavity, so provisionof through holes 35 a is particularly effective. However, in the presentinvention, such through holes 35 a are not essential. For example, ifthe thickness of the bearing inner peripheral part 36 is relativelygreat or the depth of the large diameter hole 33 a of the bearing hole33 is relatively shallow, even without such through holes 35 a,insufficient filling will not occur.

In the butterfly valve 10 according to the present invention, the largediameter hole 33 a of the bearing hole 33 of the valve body 30 is formedby the contour forming member 31 made of a plastic material without themetal core member 32 being exposed, while the bearing reinforcing part35 made of the core member 32 is arranged at the inside, that is,radially outside. For this reason, the large diameter hole 33 a of thebearing hole 33 has a sufficient corrosion resistance, while, even ifcontrolling the flow of high temperature fluid, no deformation is causedand therefore a high sealing ability can be maintained. In particular,it becomes possible to effectively keep the opening edge of the largediameter hole 33 a from deforming, so the sealing ability between theO-ring attached to the bushing 15 and the inner peripheral surface ofthe large diameter hole 33 a of course and also the sealing abilitybetween the opening edge and seat ring 12 can be reliably maintained.Further, the plastic material forming the bearing inner peripheral part36 is connected with the surrounding plastic material. This alsocontributes to keeping the large diameter hole 33 a of the bearing hole33 from deforming.

In the present embodiment, the core member 32 is exposed at the smalldiameter hole 33 b of the bearing hole 33. This is because it is usuallynot necessary to consider entry of fluid to the small diameter hole 33 bdue to the above-mentioned high sealing ability of the large diameterhole 33 a. However, in the present invention, an embodiment where notonly the large diameter hole 33 a of the bearing hole 33 of the valvebody, but also the inner peripheral surface of the small diameter hole33 b is formed from the contour forming member 31 is also possible. Inthis case, to promote the filling of the plastic material to the bearinginner peripheral part of the small diameter hole 33 b, for example, itis preferable to form the above-mentioned through hole 35 a at thecenter part 37 of the core member 32 around the small diameter hole 33 bas well. Further, in the case of an embodiment where no vertical hole 39is formed at the center part 37 of the core member 32, the smalldiameter hole 33 b is formed as a closed bottom hole, so not only theinner peripheral surface of the small diameter hole 33 b, but also thebottom surface may be formed by the contour forming member.

On the other hand, an embodiment where part of the large diameter hole33 a of the bearing hole 33, for example, just the top half, is formedby the contour forming member 31 and the remaining part of the largediameter hole 33 a is formed by the core member 32 is also possible.

Next, a first modification of the above-mentioned embodiment of thepresent invention will be explained below referring to FIG. 5 and FIG.6. Drawing (a) in FIG. 5 is a plan view of a core member 132 of thefirst modification, while drawing (b) in FIG. 5 is a sectional viewalong B-B of (a) and shows the top part of the core member 132. FIG. 6is a partial sectional front view of a top part of a valve body 130 atwhich a contour forming member 131 is formed by injection molding. Thefirst modification differs from the above-mentioned embodiment in theshape of a bearing reinforcing part 135 of the core member 132 of thevalve body 130. The bearing reinforcing part 135 of the firstmodification has a plurality of notches 135 a extending from the endface in the rotational axis R direction. In the example shown in FIG. 5,eight notches 135 a formed into rectangular shapes are provided. Due tothese notches 135 a, the inner peripheral surface and the outerperipheral surface of the bearing reinforcing part 135 are communicated,so at the time of injection molding of the contour forming member 131,the plastic material can flow through these notches 135 a and thereforefilling of the plastic material to the bearing inner peripheral part 136is promoted.

Next, a second modification of the above-mentioned embodiment of thepresent invention will be explained below while referring to FIG. 7 andFIG. 8. Drawing (a) in FIG. 7 is a plan view of a core member 232 of thesecond modification, while drawing (b) in FIG. 7 is a sectional viewalong C-C of (a) and shows the top part of the core member 232. FIG. 8is a partial sectional front view of the top part of a valve body 230 inwhich a contour forming member 231 is formed by injection molding. Abearing reinforcing part 235 of the second modification has a pluralityof grooves 235 a extending in the rotational axis R direction startingfrom the end face of the cylinder at the inner peripheral surface. Inthe example shown in FIG. 7, eight grooves 235 a having rectangularcross-sections are provided. Due to these grooves 235 a, a part with agreater thickness is formed at a bearing inner peripheral part 236 ofthe contour forming member 231. As a result, at the time of injectionmolding of the contour forming member 231, filling of the plasticmaterial to the bearing inner peripheral part 236 is promoted.

Next, a third modification of the above-mentioned embodiment of thepresent invention will be explained below while referring to FIG. 9 andFIG. 10. Drawing (a) in FIG. 9 is a plan view of a core member 332 ofthe third modification, while drawing (b) in FIG. 9 is a sectional viewalong the line D-D of (a) and shows the top part of the core member 332.FIG. 10 is a partial sectional front view of a top part of a valve body330 in which a contour forming member 331 is formed by injectionmolding. A bearing reinforcing part 335 of the third modification isexpanded in diameter continuously toward the end face of that cylinder.By the bearing reinforcing part 335 being expanded in diameter in thisway, a part with a large thickness is formed at a bearing innerperipheral part 336 of the contour forming member 331. As a result, atthe time of injection molding of the contour forming member 331, fillingof the plastic material in the bearing inner peripheral part 336 ispromoted. Further, in FIG. 9, the bearing reinforcing part 335 isexpanded in diameter continuously, but a modification in which thebearing reinforcing part 335 is expanded in diameter in steps is alsopossible.

Next, a fourth modification of the above-mentioned embodiment of thepresent invention will be explained below with reference to FIG. 11. Thefourth modification differs from the above-mentioned embodiment andmodifications in the method of production of a bearing inner peripheralpart 436. The bearing inner peripheral part 436 of a valve body 430 ofthe fourth modification is not formed by injection molding, but isformed by press-fitting a plastic bushing 436′ and melt bonding it. Forthis reason, in the fourth modification, a contour forming member 431 ofthe initial valve body 430 does not have a bearing inner peripheral part436. The bearing inner peripheral part 436 is formed by press-fittingthe plastic material bushing 436′ into the inner circumferential side ofa bearing reinforcing part 435 of a core member 432 and further by meltbonding the surrounding contour forming member 431 and the opening sideend E to form an integral unit. According to this, there is no need toconsider the fluidity or filling ability of the material at the bearinginner peripheral part. Note that, a modification where the bushing 436′is not melt bonded with the surrounding contour forming member 431, butis adhered to it to form an integral unit is also possible in thepresent invention.

Next, a fifth modification of the above-mentioned embodiment of thepresent invention will be explained below. In the fifth modification(not shown), a first large diameter hole of a first bearing hole isformed by machining. For this reason, in the fifth modification, a valvebody in which all of the first large diameter hole is filled with aplastic material at the time of injection molding of a contour formingmember is prepared, then a first large diameter hole is formed bymachining. According to this, there is no need to consider the fluidityor filling ability of the material at the bearing inner peripheral part.

In the above-mentioned embodiment and its modifications, the first largediameter hole of the first bearing hole is circular in horizontalcross-sectional shape, but an embodiment in which the horizontalcross-sectional shape is square or a D-shape or double D shape or splinehole or other noncircular shape is also possible. In this case, thefirst small diameter hole can be eliminated.

REFERENCE SIGNS LIST

-   10 butterfly valve-   11 main body-   13 first valve shaft-   14 second valve shaft-   15 bushing-   30 valve body-   31 contour forming member-   32 core member-   33 first bearing hole-   33 a first large diameter hole-   33 b first small diameter hole-   34 second bearing hole-   34 a second large diameter hole-   34 b second small diameter hole-   35 bearing reinforcing part-   35 a through hole-   36 bearing inner peripheral part

1. A butterfly valve comprising: a main body; a valve shaft; and a valvebody able to rotate with respect to the main body, wherein the valvebody is integrally formed from a core member and a contour formingmember made of a plastic material surrounding the core member to form acontour of the valve body and has a bearing hole supporting the valveshaft, the contour forming member has a bearing inner peripheral partforming at least part of an inner peripheral surface of the bearinghole, the contour forming member is continuously formed including alsothe bearing inner peripheral part, the core member has a bearingreinforcing part supporting the bearing inner peripheral part of thecontour forming member from radially outside of a rotational axis of thevalve body, and the bearing hole of the valve body comprises a largerdiameter part including an open end into which a bushing is inserted andsupporting the valve shaft through the bushing and a smaller diameterpart extending further from the larger diameter part to an inside in adirection of a rotational axis of the valve body and supporting thevalve shaft, wherein an inner peripheral surface of the larger diameterpart is formed by the contour forming member, while an inner peripheralsurface of the smaller diameter part is formed by the core member. 2.The butterfly valve according to claim 1, wherein the bearingreinforcing part of the core member has a through hole connecting aninner peripheral surface and an outer peripheral surface of the bearingreinforcing part.
 3. The butterfly valve according to claim 1, whereinthe bearing reinforcing part of the core member has a notch connectingan inner peripheral surface and an outer peripheral surface of thebearing reinforcing part.
 4. The butterfly valve according to claim 1,wherein the bearing reinforcing part of the core member has a grooveextending in substantially the rotational axis direction starting froman end face of the bearing reinforcing part in the rotational axisdirection at an inner peripheral surface of the bearing reinforcingpart.
 5. The butterfly valve according to claim 1, wherein the bearingreinforcing part of the core member is expanded in diameter continuouslyor in steps the further toward an end face of the bearing reinforcingpart in the rotational axis direction.
 6. The butterfly valve accordingto claim 2, wherein a wall thickness of the bearing inner peripheralpart of the contour forming member is smaller than a wall thickness of apart of the contour forming member at an outer circumferential side ofthe bearing reinforcing part of the core member.
 7. The butterfly valveaccording to claim 1, wherein a seal member is placed between thebearing inner peripheral part and the bushing inserted over the valveshaft.
 8. The butterfly valve according to claim 1, wherein the coremember has a rod shaped center part extending along the rotational axis,main reinforcing parts extending substantially along a plane includingthe rotational axis at the two sides of the rod shaped center part, andthe bearing reinforcing part, and the main reinforcing part is formed ina lattice shape.
 9. The butterfly valve according to claim 8, whereinthe core member is formed as a casting, the core member includes acast-in pipe member inside of the rod shaped center part, and the pipemember is comprised of a material harder than the core member.